The present invention relates to a polypropylene resin composition having excellent impact strength and stiffness for interior and exterior parts of automobiles, parts of home electric appliances and other industrial parts.
Since polypropylene resins are light and have excellent mechanical strength, they are used in various applications. However, their impact strength and heat resistance are in an antinomic relation; for instance, if the amount of an olefinic rubber is increased to improve impact strength in resin compositions for automobile bumpers, the resin compositions would have a flexural modulus lowered to about 15.times.10.sup.3 kgf/cm.sup.2 and a thermal deformation temperature lowered to about 120.degree. C. Accordingly, to maintain the strength of parts, their designs and the baking temperatures of coatings are limited. Conversely, if large amounts of inorganic fillers are added to improve stiffness and heat resistance, the impact strength of the resin compositions would drastically be reduced.
Accordingly, if such antinomy can be overcome, polypropylene resin materials would find wide varieties of applications, and increased varieties of parts would be able to be produced from one type of polypropylene material, leading to advantages in production cost.